Plyometric Training Explained In Depth

By on January 27, 2021
Plyometric and ballistic training

Plyometric training is concerned with building explosive athletes. Being strong and being explosive are not the same thing. A strong individual is someone who can move something extremely heavy from point A to point B.

An explosive individual is someone capable of running fast, changing direction quickly, and jumping high into the air. They can also deliver snappy punches, and throw things long distances. They exert strength but they do so very quickly.

A powerlifter must be strong in order to push a heavy bar. A bodybuilder must have great strength endurance to lift a heavy bar lots of times and build big muscles. Olympic lifters, sprinters, basketball players, and martial artists must be explosive.

Olympic lifters, sprinters, basketball players, and martial artists must be explosive.

How do you become more explosive, then?

The first place many people will turn to, is plyometric training. However, there is a lot of confusion surrounding what plyometric training is and what it isn’t. There’s even more confusion surrounding how to use it effectively and when to turn to other similar tools.

So, let’s jump in.

Jump. Like in plyometric box jumps. Right guys? Right?

What is Plyometric Training?

Plyometric training push up

Plyometric exercises employ rapid bursts of power with minimal ground-contact time in order to utilize the stretch shortening cycle.

An example is a countermovement jump. Here, the athlete lowers themselves rapidly (eccentric phase), pauses extremely briefly (amortization phase) then springs up into the air to land on a box or other raised platform (concentric phase).

Another example is a clapping push up, in which you lower yourself to the ground with your hands and then push up and away to launch yourself in the air. You then land again, immediately absorb the impact, then launch back up into the air once more.

The term plyometric training is a little nebulous and open to interpretation, however. In many ways, we can consider movements like the snatch to be plyometric, for example!

Plyometric Training and the Stretch Shortening Cycle

The stretch-shortening cycle means that you are lengthening and then contracting the working muscles in a very short timeframe. This is something we do intuitively all the time: such as when you “wind up” a punch.

Countermovement jump weighted

The stretch-shortening cycle is often described as being a way to tap into the stored energy that comes from stretching the muscle – like an elastic band. This is incorrect, however. In fact, the power of the stretch-shortening cycle appears to come from the time the muscle spends in the active state. This allows for more cross-bridges to form inside the muscles, thereby giving them more “traction,” as it were, to then exert force. The lengthening phase therefore acts more like a “run-up” then!

But spend too long in the stretched position and you will lose some of that potential. That’s why it is harder and not easier to jump out of a squat unless you just dropped into it very briefly! The former is an isometric-concentric movement, the latter is plyometric-concentric.

The lengthening phase therefore acts more like a “run-up” then!

This also means that the ground-contact time is actually not as important as the time the muscles spend in the active state. Thus a countermovement jump from the ground is still an example of plyometric training.

Explosive Eccentrics

That said, there is also benefit to minimizing ground contact time in other scenarios if you want to become truly explosive. Enter: the Verkhoshansky depth jump and shock training.

Plyometric training

Yuri Verkhoshansky was a successful Track and Field coach in the 1950s who also trained students from the Aeronautical Engineering Institute. He discovered that he could greatly improve jump height and other types of explosiveness by getting his athletes to exert maximum power immediately after absorbing an impact. The best example is the Verkhoshanksy depth jump. This involves jumping off of a raised platform (around 42” for maximum benefit) and then launching back off the ground after less than 0.2 seconds. This collision engages the myotatic stretch response – the sudden lengthening of the muscle causes it to rapidly contract – and this in turn allows the athlete to draw upon huge reserves of explosive strength. This same collision is also seen in sprinting and countless other movements where there are ground reaction forces.

See also: Training for Truly Explosive Strength With Explosive Eccentrics and More

How to Use Shock Training

It is not recommended to use heights above 42” until the athlete can squat 1.5 times their own bodyweight – the shock absorption involved in jumping from this height is equal to roughly 3-4X the athlete’s usual weight!

The shock absorption involved in jumping from this height is equal to roughly 3-4X the athlete’s usual weight!

Over time, practicing this type of plyometric training will increase the athlete’s eccentric strength, as well as training the CNS to anticipate the myotatic reflex and thus increase firing rate. In short: athletes get a lot more explosive and in one study, volleyball players were shown to gain a 14% increase in jump height using a depth jump program (study).

Plyometric shock training

Verkhoshansky and others have gone on to adapt shock training to other parts of the body. To turn the explosive push up into an example of shock training, we would need to jump on each repetition, while keeping the time on the ground to 0.2 seconds. All while properly absorbing the impact to avoid injury. This could translate to more explosive punching and throwing and have useful benefit for max bench press.

Not all plyometric exercises are examples of shock training. But all shock training is plyometric training.

Bouncebackability – Tendons in Plyometric Training

There are also some “rebound” elements involved in most explosive movements, however. This is where athletic properties such as ankle stiffness become important.

See also: Tendon Training for Injury Prevention and Explosive Power

Tendon hysteresis describes how pliable a tendon is (where lower hysteresis = less pliability). When running, an athlete’s calf actually plays a somewhat minimal role during plantarflexion as a lot of energy is returned by the stiffness of the tendon. Thus, it can make more sense to think of the muscles in terms of “muscle tendon units.” Fascia – the thin film-wrap that covers the muscles, organs, and more – also has elastic properties and is able to return energy to the ground. Think of it like being coated in a thin layer of Flubber.

Rest Times

Plyometric and ballistic training

One of the most crucial things to understand when utilizing plyometric training is inter-serial rest periods – rest time between sets. If you are programming plyometrics or shock training, then you should also include sufficient rest time. This is not quite as straightforward as some vocal individuals on the web would have you believe, however.

The argument goes, that in order to trigger useful adaptations with plyometrics, you need a long recovery period. This then allows the individual to exert 100% of their max effort during each rep when performing plyometrics. It has been suggested that this should be in the region of 2-5 minutes of inter-set rest.

However, other studies call into question just how strictly we should adhere to this. One study, for example, found meaningful improvements in athletes using 30, 60, and 120 second rest periods (study). The study authors noted that they used lower total volume for their training as compared with some other studies and were working with experienced soccer (*ahem* football) players.

(This article, similarly, found little difference between training with plyometrics every day versus taking a rest day in between sessions.)

Rest Times for Plyometric Training

That said, going longer during inter-serial rest periods still makes a lot of sense and this is generally standard practice (Essentials of Strength Training and Conditioning, Potach and Chu, 2008). The argument for longer rest periods is that if you don’t rest sufficiently, then you won’t be able to call upon your max effort when you perform subsequent reps of jumps. That’s the key here: max effort. Jumping as high as possible is akin to performing your one rep max: you are giving 100%. Jumping really high might still represent an 80% rep max.

Rest times in plyometric training

And this is what you need to do if you want to increase jump height and rapid force production. To jump higher, you need to create the demand for higher jumping – by regularly trying to jump as high as possible.

Thus, we should also use a similar approach to rest times and number of repetitions. Number of repetitions should be somewhere in the region of 4-5 maximum if the aim is to increase jump height, for example. And rest time should be long enough to ensure max effort the next go around.

Here’s a really great article explaining this.

Exceptions

BUT, it’s also important to realize that training plyometrics at higher rep ranges and with less recovery is not “pointless.” For one, this trains the ability to call upon explosive force even in a fatigued state. This, of course, is how we are often required to be explosive in sports and in life. A series of 20 tuck jumps, performed three times, with 30 seconds of rest is great for an athlete that is required to be explosive for long durations and will still offer some increase in jump height most likely. This will also help to stiffen those tendons, allow the necessary neural pathways to form, and build isometric strength and stability in all the right places.

Lifting 85%+ of your 1RM is most likely going to deliver the best strength gains. But bodybuilders get stronger using lighter weights too.

Just take a look at Grant who uses lots of bodyweight conditioning movements like this. He’s about the most explosive guy I know in real life!

More Factors

The number of repetitions is also limited by the amount of time we can spend performing a set of plyometrics. After all, this is a form of training that utilizes the phosphagen or ATP-CP system for rapid energy release. That means we can’t maintain good effort for much longer than 10 seconds.

How many reps can you cram into that time? To answer that, we must also consider the “intra-serial” rest time. In other words: how long should you pause between each repetition? We already know the answer if we’re talking about depth jumps and other shock training – 0.2 seconds. Otherwise, the intra-serial rest will be determined by the nature of the exercise: there is an unavoidable rest period in countermovement jumps, for example.

This trains the ability to call upon explosive force even in a fatigued state.

Of course, fatigue also increases the likelihood of injury. This is particularly important in any exercise that involves leaping off of heights and absorbing large amounts of shock. Should the athlete slip or allow their knee to collapse inward, it’s game over.

(This is true in general when using plyometrics and especially box jumps. Make sure that there are no valgus knees and that you are properly absorbing the shock as you land).

Complex Training

We can also combine plyometric training with strength training. The problem with strength training for increasing running speed, is that the ground-contact time for a sprinter is around 90 milliseconds. This is not enough time to tap into max strength, and so the rate of force development is more important: the rate at which the sprinter can generate power.

Complex training

It’s combining plyometrics with strength training that will result in the greatest rapid recruitment of Type 2 muscle fibers. Complex training therefore combines strength training with a “matched” plyometric movement. For example, you may perform bench press followed by explosive push-ups, or squats followed by countermovement jumps.

It’s combining plyometrics with strength training that will result in the greatest rapid recruitment of Type 2 muscle fibers.  

Complex training appears to work via post-activation potentiation. This means that the muscle fibers and nerves are “primed” for action. This is the same reason that you feel super light jumping after you have been squatting with a weighted vest.

The neurons and spinal nerves that coordinate the movement don’t return to their previous resting potential, meaning a weaker signal is required to reactivate them. It’s also postulated that the actin and myosin within the muscles become more sensitive to calcium from the sarcoplasmic reticulum.

According to one study, the optimal rest period between these is 3-4 minutes (study). Generally, it is performed with reps using roughly 85% of the 1RM followed by lighter plyometrics. This is an advanced technique and not necessary for most people!

Ballistic Training

As you can see, this is not a straightforward topic! And the similarity between, plyometric movements, shock training, and other forms of training can lead to a lot of confusion.

Plyometric training is not the only way to increase explosiveness. Take the kettlebell, for example. Swinging a kettlebell is an example of ballistic training. This is about acceleration and power, but without the stretch-shortening component.

Bulgarian Bag - Functional Training Tool

See also: The Many Facets of Kettlebell Training

Does this still build explosiveness? In a word: yes!

Any time you are required to generate force against resistance and the aim is velocity, you are developing power and explosiveness. But this doesn’t necessarily make it plyometric training.

More specifically, you are working on “rate of force development.” This means you are training yourself to recruit muscle fibers quickly, which is what you need when operating in nearly any athletic environment. Being strong slowly is only really useful in weightlifting competitions.

(That said, if you use the “overspeed kettlebell swing,” where the aim is to pull the weight back down as quickly and powerfully as possible, then you will be engaging in something akin to a form of shock training! This also involves less impact on the joints and thus can be used more liberally.)

Bar Speed and Rate of Force Development

Even among powerlifters: aiming to move the bar quickly during strength training will recruit more type 2x muscle fibers, which will result in faster strength gains. Those are the ones you need if you’re trying to exert maximum force. In short, it’s as though you are adding just a little bit extra weight onto the bar.

Bar speed

This is also why we see strength athletes using “compensatory acceleration.” Here, they practice using lighter weights on some days but combine that with greater acceleration. The Westside Barbell System refers to this as the “Dynamic Effort Method.” Ideally, you should train using 50-70% (Supertraining) of your one-rep maximum and to thus increase neural drive, giving you greater control over your strength and allowing you to explode out of the bottom of a given movement. This has similarities with plyometric training (especially if you bounce a barbell off your chest).

That is why “bar speed” is such a useful measure, too. Coaches will look at how quickly an athlete is moving the weight and adjust accordingly.

The problem is that when the weight is too heavy, we are not able to move with enough speed. The intent changes. We are now “grinding” through the movement.

If your squat max is going up but your vertical is staying the same: try the dynamic effort method.

See also: How to Get Stronger – Hulk Training

Getting the Resistance Right

This is also why sprinters training with the sled pull saw improvements in their running speed until they upped the total amount to beyond 75% of bodyweight (study).

And this is another very important point to consider: relative strength. The lighter you are, the less max strength you need in order to move explosively. Your programming should thus revolve around that specific trait.

The Mental Game

What should be standing out here is that plyometric training is very much mental game. It’s all about the intent with which you perform the movement. If you aim to “get through” a set of push-ups, the results will be very different than if you aim to perform them as quickly as powerfully as possible. Likewise, if you “grind out” reps of a bench press, you’ll increase max strength, control, and strength endurance. But “explode” out of the lift and you’ll increase rate of force development. As usual, I want to be good at everything.

Plyometric training

It doesn’t even matter if you move! You can increase rate of force development using ballistic isometrics, too. These involve pushing or pulling explosively against an immovable object as quickly as you can. This could be another effective tool for contrast training that would minimize fatigue if used correctly.

This is also why it can be useful to train using some kind of external cue if you want to develop true explosiveness. Strength is useless in a vacuum, so why not aim to jump on command: get a spotter to blow a whistle at random intervals so that you can exert that power as quickly as possible. You could even use two different tones in order to learn both reaction and action suppression. This is, once again, where plyometric training goes from theoretical and detached, to genuinely useful and applicable.

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About Adam Sinicki

Adam Sinicki, AKA The Bioneer, is a writer, personal trainer, author, entrepreneur, and web developer. I've been writing about health, psychology, and fitness for the past 10+ years and have a fascination with the limits of human performance. When I'm not running my online businesses or training, I love sandwiches, computer games, comics, and hanging out with my family.

3 Comments

  1. Andrew Smee says:

    Hi ,where did you get your slam ball and what make is it as I need one for a hard surface.Thank you Andrew Smee.

  2. subby says:

    can you make a training programme for beginners

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